319
CHAPTER NINE
Muscular System
epicondyle of the humerus, one from the medial side of the
ulna, and one from the radius. It is inserted in the tendons of
the F
ngers and fl exes the F
ngers and, by a combined action,
exes the wrist (see F
g. 9.32).
Some of the F
rst signs of Parkinson disease appear in the hands. In this
disorder, certain brain cells degenerate and damage nerve cells that
control muscles. Once called “shaking palsy,” the disease often begins
with a hand tremor that resembles the motion of rolling a marble
between the thumb and foreF
nger. Another sign is called “cogwheel
rigidity.” When a doctor rotates the patient’s hand in an arc, the hand
resists the movement and then jerks, like the cogs in a gear.
ulna to carpal and metacarpal bones. It fl exes the wrist and
adducts the hand (see F
g. 9.32).
The
palmaris longus
(pal-ma
ris long
gus) is a slender
muscle located on the medial side of the forearm between
the fl
exor carpi radialis and the fl
exor carpi ulnaris. It con-
nects the distal end of the humerus to fascia of the palm and
fl exes the wrist (see F
g. 9.32).
The
exor digitorum profundus
(fl ek
sor dij
ı
˘-to
rum
pro-fun
dus) is a large muscle that connects the ulna to the
distal phalanges. It fl
exes the distal joints of the F
ngers, as
when a F
st is made (see F
g. 9.34).
The
exor digitorum superF
cialis
(fl ek
sor dij
ı˘-to
rum
su
per-F sh
e-a
lis) is a large muscle located beneath the fl exor
carpi ulnaris. It arises by three heads—one from the medial
Abductor pollicis longus m.
Flexor pollicis longus m.
Radius
Extensor carpi
radialis brevis m.
Extensor carpi
radialis longus m.
Pronator teres m.
Brachioradialis m.
Radial n.
Radial a.
Flexor carpi radialis m.
Extensor digitorum m.
Extensor carpi
ulnaris m.
Extensor pollicis
longus m.
Ulna
Flexor digitorum
profundus m.
Ulnar n.
Ulnar a.
Flexor carpi ulnaris m.
Median n.
Flexor digitorum
superficialis m.
Palmaris longus m.
Plane of
section
Anterior
FIGURE 9.34
A cross section of the forearm (superior view). (
a.
stands for artery,
m.
stands for muscle, and
n.
stands for nerve.)
TABLE
9.9
|
Muscles That Move the Hand
Muscle
Origin
Insertion
Action
Nerve Supply
±lexor carpi radialis
Medial epicondyle of humerus
Base of second and third
metacarpals
±lexes wrist and abducts hand
Median n.
±lexor carpi ulnaris
Medial epicondyle of humerus and
olecranon process
Carpal and metacarpal
bones
±lexes wrist and adducts hand
Ulnar n.
Palmaris longus
Medial epicondyle of humerus
±ascia of palm
±lexes wrist
Median n.
±lexor digitorum profundus
Anterior surface of ulna
Bases of distal phalanges
in F
ngers 2–5
±lexes distal joints of F
ngers
Median and ulnar nerves
±lexor digitorum superF
cialis
Medial epicondyle of humerus,
coronoid process of ulna, and radius
Tendons of F
ngers
±lexes F
ngers and wrist
Median n.
Extensor carpi radialis longus
Distal end of humerus
Base of second metacarpal
Extends wrist and abducts hand
Radial n.
Extensor carpi radialis brevis
Lateral epicondyle of humerus
Base of second and third
metacarpals
Extends wrist and abducts hand
Radial n.
Extensor carpi ulnaris
Lateral epicondyle of humerus
Base of F
fth metacarpal
Extends wrist and adducts hand
Radial n.
Extensor digitorum
Lateral epicondyle of humerus
Posterior surface of
phalanges in F
ngers 2–5
Extends F
ngers
Radial n.
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